1. Field of the Invention
The present invention relates to an apparatus for regulating output voltages and, more particularly, to an apparatus for regulating and outputting DC voltages.
2. Description of Related Art
An electronic device (e.g., a chip) usually requires at least one DC power source. In consideration of the working voltage and power consumption, several DC sources (e.g., 5V, 3.3V, 2.5V and 1.8V) are usually used. Linear regulators and switch regulators are commonly utilized to generate a plurality of DC voltages. The linear regulators are generally used in situations that require more precise voltages without the need of considering the power consumption. The switch regulators, on the other hand, apply to situations that take power consumption into consideration without the need of precise voltages.
In order to give consideration to both the power consumption and precise voltages, a DC to DC converter is adopted to convert a DC voltage to the required DC voltage. The DC to DC converter, however, requires a plurality of inductors and a plurality of control circuits to achieve a plurality of DC voltage outputs, hence resulting in large chip size and increase of cost.
In order to solve the above problems, U.S. Pat. No. 6,204,651 provides a method and apparatus for regulating output voltages of a switch mode regulator. In the proposed method, a representation of the DC output voltage is first compared with a reference voltage to produce a digital stream of comparison data. The comparison is done at a given clock rate such that the digital stream of comparison data is produced at the corresponding clock rate. The digital stream of comparison data is then interpreted to produce a digital stream of charged data and load data. Next, the digital stream of charge data and load data are interpreted to determine, for a given set of clock cycles, a charge signal and a load signal. Charging of an external element (e.g., an inductor) is enabled in accordance with a charge signal for the given set of clock cycles, and discharging of the external elements to a load (e.g., a capacitor) is also enabled in accordance with the load signal for the given set of clock cycles, accomplishing the function of regulating the output voltages.
The above method, however, cannot handle the current mode. Moreover, the problem of overcharge may arise during the charging process.